Aurelian Walls

19 kilometres of fortifications built by Emperor Aurelian between 271 and 275 AD — Rome's response to a series of barbarian raids that had finally pierced its old illusion of invulnerability. Constructed in just five years using forced labour and reusing existing buildings as wall sections, they remained the city's primary defense for 1,600 years. Most of the wall survives intact, and at Porta San Sebastiano you can climb up and walk along a preserved section through the small Museo delle Mura.